Pressure combustion and compressor



July 29, 1952 LOVE 2,604,934

PRESSURE COMBUSTION AND COMPRESSOR Filed Nov. 3, 1944 2 SHEETS-SHEET l INVENTOR July 29, 1952 LOVE 2,604,934

PRESSURE COMBUSTION AND COMPRESSOR Filed Nov. 3, 1944 2 SHEETS-SHEET 2 llfigfl 15 e o SPARK PLUG To lNlT/ATE' COMBUSTION 44 5754M OUTLET r b F/ g. 1/1. 0 fEEa Wmm llw. [T

INVENTOR Patented July 29, 1952 T 2,604,934 v, i '1 PRESSURE iCOMBUSTIONAND ooMPRE ssjo'R Ben Love;.Garnegie-,*;Par i Application November 3, 1944; seriarm;56137 .1

4' Claims;

Mi n ention'reiatesto particularly; though, not, exc1usivel'y,jto the" com pressing ,of :air for; sustaining combustion ofifuel under superatmospheric, pressure; 'I'h'e' "inven= tion consistsin. certainrnewiandiuseiiil' 'improve ments in method ,..andi iniapparatus", ,and."chiei among,.-m objects are the; obtainment 'of in: crased..efii'ciency. andlIeconomy in, the. compressioni ofgas; and. increasedconservation e and utiliiationlofl the energyfproduced byathe jcom bustionof-fue1.- The invention will be understood i upon refer ence tolaccompanying -drawings',,in-whicli:

Figure I is! a. diagrammatic -.v-iew= of laniexeinplary reciprocating engine, .in' which .and'in, the

operationofwwhichi the. objects .v of themvenno'n may. be i realized, the View showing the l engine partly in side elevationrand. partlyinryertial ci na; or r e 7 Figures II, III and are viewsv comparable with Figure ,I, severally illustrating;successive.

stagesin; the reciprocation 011 ithelrpistonof. the i k. v

, Figure V- issa timingg diagram; of-- thewalves; of the engine;

Figure VI iS a diagrammatic lview with oer..-

tain i arts shown in verticals section oreteam generatinggapparatusinwhich my. improvements in I pressure combustion are;- incorporated and utilized;

FigureVIIis aediagrammaticr-view in.perspective of: a valvemeehanism eof :the--oompressor engine-yand I 7 Figure VIII showsthree cross sectional views ofa valve-operatingoamofithewalve mechanism,

the view s :being. takenorespectively. onv planes normal to theaxis of thecamshaftpas indicated by-thelinesa; b and c in Figure VII. 7

In. general it..is to he understoodhthatihitherto it has. been proposed to -.inti'.oduce,charges ofga's 1(orvapor.) atsuper-atmospheric pressure to. the cylinders 10f e reciprocating engine, and, 5. by; the expansion of .such. charg s. in theicylinders, ,to drivethe pistons .of thewenginehlandmaintain thern in .reciprocation. Alternatelginwith respect to the cyc lesvof the-pistons, during ,which the charges. of gasvare introducedlto ether .engineroyl index-"s and expanded-Q voharges of. Iaiim (or. .other gas tobe coin-pressed) are'introduced to thercyl inders and compressed by the so-dri venpi'stons.

Thusitis that the-same cylinders-and 1pistons of the engine are utilized-both aso-airi-compressing instrumentalities andwas the operating motor therefor...

I .It'. will beunderstoodl that. during ,theicompresethe'compressingpf gas;

si'omofthe successiveair charges; heat 'is gener atd and yielded to-the walls' of the engine} as evidenoed -hyy'the usual-' practice of providing water" jackets upon the oylinders of--'high-f pressure air*compressors}tofprevent" them Hom becoming---recl- -Hoff-and failing:- Conversely; inthe expansionot the successivecharges of power gas heat-is -consumedi- Of-- course, in the usual internal combustion engine; the -tempera-tur'es fde veloped by the exploding iuel charges-are so high that the=heat-1oss due- -toth expansion ofthe burningchargesis *novadequate to keep-t-he engine "walls sufiiciently-cool" without" the"aid of a watewjacket, hr -cooling gair circulated over 'the external walls 'ofthe'engine. V

The xpractice of my inven tion involves *the use of c'zl'iarg'esiiofpower gas-orwapor' at a relatively low-temperature; "wh-ereby gthe" expanded 'charges are eife'ctiveiito 3.-bSOIb.hBJt "impartedztd the 'en" gine walls during ,the' "compression '01" the' air charges:heat"which'*is' otherwise. dissipated and lost; In" accordanceiwith ,the' invention, I estab= lislfand maintainsubstantially a thermal balance loetween the "heat "which is yielded to the enginewallsildytheicompression "of the air charges and the::heat which i'sjabsorbedirbritsuch walls byihe expansion .ofth' charges of'p ower gas.

The heatyijelded totliexpiston body and cylinder walls duringjhecompression" of each charge of air,"'is taken up by; the next-ensuing"charge. of

powergas inoourse ,ofiexpansion. Thus, the heat a savingsin the cost -ofjequipment, but I- more nearly approach" the mean conditions of" thermal efiTci'enc T achieVing, as the physicist would'say; a close approximation ofjan adiabati"c,.cyc1e.

Referring; to the/accompanying; drawings a reciprocatiii'gifengine,isindioated bjthereference numeral 15".; For. simplicity in description and-i lustration .the-en"gi"ne 515 shown .to-ibe ar single cynnderengina. and 'its' Valves: are diagrammaticallyg indicated, 'with the valve springs; and the valve-operating gear omitted, but with" the understanding that the .valves and their-springs and; operating ear. Tas hereinafter set' f orth,'. will be so particularly designed as; to admit 'ofthe operation presentlyjfto' be described. Thegas (or vapor),,which1under superatmospheric pressure drives thelengin'e, enterseth cylinder 1 ll by way-gotten .iiiile'tipipe I ll? leading from L a. .source crankshaft rotation by the angle a, Figure V),

the inlet valve I4 is closed, and the charge of gas in the cylinder expands, driving the piston through the remainder of its downward stroke, and imparting rotational momentum to they flywheel (not shown) and other rotating parts of the engine. As the descending piston passes from the position in which it is shown in Figure II to that in which it is shown in Figure III, theexhaust port it opens, and, the spent gas is exhausted. The exhaust port of the engine consists in a circumferential opening is in the wall of the cylinder, and such opening [6 stands in immediate communication with an exhaust chest ll connected to an exhaust duct I10. fdesired, suction-producing instrumentalities, such asan exhaust-pump (not shown), may be organized with the exhaust duct. 7 I

The air to be compressed in the cylinder is introduced through a duct i8, and is subject to the control of an air inlet valve l3. Advantageously, the air is supercharged, thatis, it is fed at superatmospheric pressure into the engine, the means to such end consisting in this case of a cycloidal pump I80, geared in manifest way to the rotating shaft of the engine. Upon the opening of the exhaust port l6 by the downwardly moving piston 12, the "air inlet valve l3 opens (of. Figure IE). The air streams into the cylinder and sweeps the spent power gas therefrom, and fills the cylinder-with a charge of air. The piston [2 (under the influence of the energy stored in the rotating parts 7 of the engine) moves upward, and the air valve l3 and exhaust port l6 close (Figure IV), and the charge of air is compressed. Preferab y, the air valve closes after the exhaust port closes, whereby a substantial supercharging of air is obtained. The compressed air is fed from the engine to a receiver, or other point of disposal, by means of a discharge duct 6. Communica tion between the duct 6 and cylinder H is subject to a check valve N that is normally'held in closed position, save under the conditions now to be described. When the rising pressure of the air being compressed by the upwardly moving piston l2 reaches and slightly exceeds the pressure prevailing in the ductG, the checkvalve I9 is forced open, and the compressed air is discharged. As the piston reaches theupper end of its stroke (Figure I), the inlet valve 14 again opens, and a charge of power gas is again fed from pipe it! into the cylinder. Such is the operation of the engine in one complete reciprocation of the piston. Of course, in service the operation is repeated, and continues without interruption. f i

v The heat of compression yielded to, and conserved in, the cylinder walls by each air charge is, through the expansion of the next-succeeding charge of power gas, removed from the cylinder walls, with the good effects already described. The engine is enclosed in a heat in sulating jacket 50, Figure'I, such jacket providing in this case the means for inhibiting the loss of heat from the engine, to the end that the thermal cycle described may be established and maintained.

It will be manifest to persons skilled in the art that many modifications and variations of the method and apparatus described may be utilized, without departing from the essence of the invention." For example, the air-compressing engine has been illustrated and described as a two-cycle engine: Manifestly a four-cycle engine of generally known sort may be adapted to serve.

It will be understood that the invention will prove valuable in many and widely varied fields of industry. The power gas employed may be steam, or the products of combustion of apparatus in which fuel is burned under superatmospheric pressure, or any other suitable gaseous orv vaporous medium under superatmospheric pressure. The invention is not limited to. the particular source from which the power gas is obtained. Again,airis not the only gas which may be compressed in the engine. Indeed, it is contemplated that the invention may be applied in the generation and compression of carbon dioxide in the manufacture of Dry Ice; and various other uses will be found in various fields of industry. However, as mentioned in the forepart of this specificatiom'my method is particularly adapted for the combustion of fuel under superatmospheric pressure, and in such field I shall describe an elaboration of the invention.

' Referring to Figure VI, I show a heat exchanger, in this case a steam generator, which is fired under superatmospheric pressure. The generator includes a boiler l, a combustion chamber or fire-box 2, and a fine outlet 3. Fuel and compressed air are introduced to the firebox through an injector 4, and combustion under superatmospheric pressures up to ten atmospheres or more is sustained in the fire-box. Herein fuel oil provides the fuel, and a jet of such fuel, together with compressed air delivered by a pipe 6, is projected into the firebox against an incandescent wall or baille 2a ofrefractory material. -The hot body of the baffle 2a. insures the cracking of the hydrocarbons in the fuel, and consequently the complete combustion of the fuel.

It will be understood that at high pressures the quantity of heat contained at given temperature in a unit volume of gases greatly exceeds the heat contained in the same volume of gases at the same temperature, but at substantially normal atmospheric pressure, and because of such greater heat content per unit volume of gas, plus the fact that heat transfer from the fiames and hot gases under the higher pressure is more rapid than under the normal lower pressure, the required'heat-transfer surface of a boiler of a given output rating may be much smaller in area than is otherwise possible. Accordingly, a pressure-combustion boiler may be 'minimized "in size for a given boiler rating- In the lighter these circumstances, I have conceived an improved pressure-combustion boiler, and have'provided a particularly effective organization of such boiler with the compressor.

As'illustrated in Figure VI the boiler l is double walled throughout its cylindrical sides and domeshaped top, forming between the two walls a container for a body la of liquid of high vaporizing point, such as mercury, or a low-melting- Jpointmetal, or other; suitable material.- In such body the boiler tubes 20.. are submerged; i The water or other li'quid of relativelyz low boiling point, tozbei-convertedlinto steam isinjecte'd; The boiler tubes 20 this case comprise a helical coil of steel tubing, having-a feediwater inlet 201) at the lower end of thelcoil land a steamoutlet 20a at-the upper end, as illustrated. Theiheat generated by combustion within the fire-box -2 .is transferred to the bath of-mercuryand the boiler tubing submerged therein. The waterintroduced to the boilertubing is converted to steam, which is-delivered through outlet 20a. An advantage-of this use of mercury, or the like, is that allof the surface of the boiler tubing i'sheated unifor-ml'y; whereby the tendency for hot spotsto develop is minimized; Theproblem :of 'lb'oiler water treatment (to eliminate:the' forniation of boiler scaleon the inner surface :of the -tubing) issimplified if not eliminated; since any pre cipitates form'ing in the i boiler tubing are carried outof the tubing by the-high-pressure steamo The boiling point of;mercury is 1 approximately 675 -F., and at this-temperature*saturated steam has apressure of :about 2600 pound's: per square inch, apressure .too high for usual industrialapplications. However, the boiler' -is :operated as a flash? boiler, in which :the quantity. of-' water supplied to the boiler tubing is=regulated'to main tainthe steam pressure at any-desired: practical 'pressure, -say a pressure-unto 12U0'pounds. This saturated steam at-1200 pounds pressure has-a temperature of only 567 :F.,'Lwhile the :temperature of the mercury" may; and ordinaril-yi willl be,

substantially higher, withthe: 'elfec't that 'the steam generated at 1200 pounds 'Lpres'sure in the boiler-will:besuperheated.

order to promote uniform temperature throughout the body of mercury, as -well as to expedite heat transfer thereto from-the hot flames and gases within the pressure-combustionchamber' or fire-box -Z, I provide banks .of vertic'altubes "lc 'that interconnectxthe top and bottom portions 'of the confined body of mercury; Thelbanks iof tubes extend intothe fire bomfas:shown; The banks of tubes are provided throughoutithe :cir'- cumference or 'the fire-box, "and promote maxi:- mum hea't absorptionzby the-mercury; The':iiames and --'hot products of combustion orsgases frebound from the incandescent 'baffi'e' i241 against 'which the fuel jet plays, :and sweep upward in spreadin'gstream Iover andabetwe'en the tubes :as

indicated by the dotted arrows; A thermally induced circulation of the mercury'is thus-main tainedt 5 As the upwardlyiflowing gases reach the top of the firebox 'they flow-to the outletf3,sweepingagainst the inner of two wallsotthe boiler body. v a

The body of mercury Ia does-not fill the'space between the two-walls of the boiler body, but 'has'its level 'at such plane lbthat a space for mercury vapor-isprovided at the top o'f the firebox, it being'noted that mercury vaporis generated in the operation of the boilen and is sealed or confined in this-space. As will presently appear; thepressure of this mercury vapor isutilized in'efiecting a control of certain phases-of the operation of the apparatus.

The compressed-air for sustaining combustion inftheffire-box 2 is, as has been said; delivered to the injector l-by means of the-compressed air line 6 extending from the-engine 5. The fueloil isidelivered to "the injector througha pipe 1 leading from a supply'tank'tl. A branch line 9'extends from the compressed air lineto-the fueltank-so -thele'ss at a superatmospherie temperature; in

thiscase a temperature substantially in excess of 675 The inlet duct N1 of the engi'ne is con-'- nected 'to --the outlet 3 0f the steamgenerator.

Desirably the-apparatus willb'eso designed'and the parts so proportioned and operatedthat-all of the productsof combustion generated-in the fire-box will be utilized in driving the air com pressing engine. If, however, the productsofcombustion should in-some cases exceed the requirements of the'engine, a safety valve 20 will open and relieve the excess pressure. 1 The efiect of this safety valve will also serve in conjunction with-'thevalve mec'hanism described belowto govern or limit the maximum speed" of theen- In starting the operation-of-theapparatus; the air-compressing engine 'may be driven by com pressed air delivered from any suitable source'to the'-pip'e l0 Alternatively,an electric starting motor, such as the'motor normally used in startinganautomobile engine,-may"be used. In order that the startingmotorneed'not berununtil the boiler is brought up to-operating temperature, I provide a branch'pip'e I00 that leads fromthe fire-box to a valve-chest I01 included in the duct Hi.- When the apparatus is being, set in operation the duct I 0 above the valve-chest is dosed, and' t-he hot products of combustion arepassed immediately from fire-box (before they have yielded heat to the'heatexchange elements-of the boiler) to thechest l0! and'thence 'to the airs-compressing engirre t, whereby' the engine is adapted more quickly to'-be brought up to: the point for operation by-the wastegases of r the boiler; As the-fire-box and boiler approach normal operating temperatures, the duct 10 above "the 'valve-chestdsgradually opened -and the branch I00 gradually closed. The'apparatus is thus set in normal-operation. I

Means may be provided for accomplishing all of this automatically. In exemplary-way, I provide in the valve-chest H]! a diaphragm or bellows device 102, which is adapted to expand and contract and to shift a stem HM according as the temperature within the chest Ill] rises and falls. Thestem I04 is articulated to the upper end of a lever I05, and such lever carries a valve-block 103 that is adapted to control the flow or the waste gases from ducts ln'and Hill. When the apparatus is being brought upto normal operation, the temperature induct Ill, is low,

'delivered tothe engine =5. l.'As thetemperatures and pressures within the. system approach o'per atingvalues, the valve 103: is graduallyreturned tonormal position, .closing the branch 100' and openingtheline, I0. A

If any .of the heat' generated by pression of theair charges in the engine is not takenv up by the-engine body, it is retained by the air fed to thefire-box, giving the efiect of preheating the air for combustion: .It will be seen that the power gas (products of combustion) which drives the engine mustcontain more heat or pressure energy than that which is needed for the compression of the air, to compensate for the unavoidable friction, etc., losses encountered ;in the operation of the engine. Theinlet temperature and pressure, of the products of combustion or power gas will in the main control the pressure to which the aircharges may be compressed, and the compression, temperature in the engine will approach the; temperature of such power gas, there beinga temperature differential due to said losses in the engine.

If, in the normaloperation of the system, the pressure of the waste gases of the steam generator should suddenly fall below effective value (due -to a sudden and extraordinary withdrawal of steam from the boiler), the temperature, of the gases flowing through chest falls and the mechanism in the chest operates to shift the valve I03, thereby short-circuiting hot gases from the fire-box-to the engine 5, and accelerating engine operation. However, in order to maintain theapparatus in the state of operation inwhich the heat yieldedto the engine walls during the compression of the air charges substantially equals the heat absorbed from such walls during the expansion of the charges of power gas, another device (and in many-casessuch deviceis self sufficient), is provided for the automatic regulation of'the quantity of gas in'the power gas charges relatively to'the quantity of air in the air' charges. In this case such effect isgained by holding the air charges substantially uniform, while automatically increasingor decreasing the individual power gas charges; In a Before describing such device in detail,;atten,- tion will be directed to thevalve -timing diagram of Figure V. The sequential operation of the valves l3, l4, l6 and I9 oftheengine are respectively denoted bythe arcs c,,a, b and cl. .;While I have indicated thatthe air inlet valve 13 opens at thesame instant as'the exhaust port lfiopens, it is to be noted that the air inlet valve may open either immediately before or immediately after the exhaust port opens. And it will be understood that the difference between the angles b and c in the valve diagramof Fig. V indicates the interval of lag between the closing of the exhaust port and thefclosingof the air inlet valve, in which interval; the supercharging of air into the cylinder is effected. The power gas valve 14 and the air valve 13 may be severally operated by means of rocker-arms cooperating with cams on a cam shaft geared in known manner to be driven from the rotating crank-shaft of the engine, and

by elaboration ofknown valve mechanism of this general type, or the like, the timing of the power gas inlet valve relatively to that of the air inlet valve maybe automatically modified, for the purpose mentioned. 41

Turning to Figure VII the cam shaft 38 of the valve mechanism is indicated. The shaft is journaled for rotation in bearings 3 I, and is equipped with a gear 32 that meshes with the conventional .cam-shaftxidrive; (not; shown). of .the engine.

'swingon its pivot; and toropen and close the power gas .valve. l4, :under:the.- effectof a tension spring 35;,and;..a,cam iii-engaging, asthe shaft rotates, the. roller-equipped distal end of the rocker arm. It: will be understood that a similar rockeriarm, device is arranged to open and close the .air valve' l3, onlythe gas-valveeoperating cam 3'!v being shown The cam shaft is journaled not only for rotation in the bearings 3|, but for axial movementas welL-a feathered or splined slidingunion being providedbetween the shaft and gear32'. I

,Both of the cams36 and 31 are elongate, extending axially of; the shaft, so that the valveoperating rockersof-both valves l3 and I; may remain in valve-operating engagementwith the cams as the cam shaft isaxially shifted, as it is, by means of a lever 38, pivoted intermediate, its ends to a stationary post 39, and engaged on one side of the pivot between two collars 40 fixedto therotary shaft, and on opposite side of the pivot by atension spring 44' and the plungersof two metallic bellows 42;and 43. The interior of the bellows 42 rcommunicates through tube 44 with the mercury vapor chest at the top ofthe steam generator, while the-be1lows43 is similarly connected bya tube 45 totheinterior of the combustion chamber or fire-box 2. ,Norma1ly, the aggregate thrust ofthe plungers of the two bellows, produced by the cumulative effectof the pressures prevailing in the mercury vapor chest andthe fire-box,is equal and opposite to the effect of spring. tension upon the lever 38, whereby the shaft rotates in an. intermediate position in its range of axial movement. When this condition obtains, the'power gas charges bear a constant relation to the air charges, such arelation as produces andmaintains the described thermal balance within the engine. a On the other hand, when the conditions of operation of the steam generator change, .due'to variations in the demand for steam and for change in firing rate, or any other reason, the physical condition (pressure and/or temperature) of the waste gases vary; and the aggregate effect of the pressures :acting upon the-bellows 42 and 43 is increased or decreased,-as the case may be; the lever 38 swings in one direction or the other and corresponding ly shifts :the cam shaft axially; Whereas the cam ,3! that operates the air valve isof uniform throw-throughoutaits extent, the throw of. the cam 36is varied .longitudinallyof the shaft, from a maximum throw at its right-hand, FigureVII,

to a zero or substantially zeroth'row at its lefthand end; of. the cross sections a, b and c in Figure VIII. While there is this variation in the throw of the cam 36, it is to be noted that the point p at which; the cam initiates the opening of the power gas valve l4 bears aconstant relation to theaxis of the shaft throughout the extent of the cam. From the foregoing it will be seen that the durationof opening of the air-valve, and the quantity of air in the successive air chargesadmitted to the engine, remain constant throughout the range of shift of the cam shaft, while the duration of opening of the power gas valve is varied, with consequent variation in the quantity of gas in thepower gas charges introduced to the engine. When the heat or intrinsic energy in combustion gases drops below a normal value, the .fact is refiecte d'in a, drop in pressure ineither or both ofthe bellows42 and 43,'w,i th t 'e ss e rhe crewm n: lever 38 and shifts the shaft 30 in right-to-left direction and increases the effective throw of the cam 36 which in turn is effective to increase the duration of opening of the power gas valve l4. The quantity of power gas admitted to the engine in each charge is increased to maintain the thermal balance. Conversely, when the heat of the products of combustion rises above normal value, the pressures effective in the bellows predominate over the tension of spring 4|, and the lever swings and shifts the shaft in left-to-right direction, reducing the efiective throw of the cam 36 and reducing the quantity of gas in the engine-driving charges, to maintain the thermal balance.

Such is the construction and mode of operation of a pressure-combustion apparatus of my invention. And it will be perceived that if the power gas or vapor for operating the compressor engine 5 be some other medium than the products of a pressure combustion system, a regulation of the power gas or vapor may, in the light of this disclosure, be provided by the engineer.

It remains to be noted that where it is desirable to operate the steam generator described at temperatures lower than those required to produce mercury vapor at substantial superatmospheric pressure in the chest at the top of the fire-box 2, a fluid lighter than, and having a lower vaporizing point than, mercury may be provided on top of the body la of mercury in the boiler unit. Such a known liquid as Dowtherme, or certain petroleum distillates of higher boiling point than water, may be mentioned in exemplary way. It will also be understood that the conventional Water tube boiler may be used in the place of the steam generator disclosed herein, and may be arranged to be fired by pressure combustion, such for example as the boiler shown in Letters Patent No. 2,227,666 granted January 7, 1941, to one W. G. Noack, and the connection 44 for the bellows 42 of my apparatus may be made at a point exposed to the steam pressure in such boiler.

The rocker-arm valve mechanism described in the foregoing specification is illustrative of the several known equivalent valve mechanismsthat the engineer may adapt to the operation of the air and power gas valves of the engine in the manner and for the purpose indicated. These and other modifications are within the spirit of the invention defined in the appended claims.

In Figures I and VI, I show the engine 5 to be covered with an insulating jacket 50, and it will be manifest that the steam generator I and the entire system of ducts and tubes 6, I0, 44, 45, I00 and llll may be incased with insulation.

The application for this patent comprised a continuation-in-part of an application, Serial No. 393,996, filed by me May 17, 1941, and now abandoned.

I claim as my invention:

1. In an expansible-chamber heat engine and gas compressor including a cylinder and a piston reciprocable therein, a connection to a source of power gas, a valve controlling admission of gas from said source to said cylinder, an exhaust port for relieving expanded power gas from said cylinder, a connection to a source of another gas to be compressed, a1valve. controlling admission of said other gas to said cylinder, a connection to said cylinder for delivering said other gas to a point of use when compressed, means periodically opening said first-mentioned valve and means responsive to the increase or decrease in pressure of the power gas for adjusting the valve-opening means to conversely decrease or increase the time during which the valve is held open.

2. In an expansible-chamber heat engine including a cylinder and a piston reciprocable therein, a combustion chamber and a valve controlling the admission of fluid from the chamber to the cylinder, the combination therewith of a mechanism for periodically opening said valve for a variablelength of time, means for adjusting said mechanism to vary the length of time the valve is held open and means responsive to the increase or decrease in pressure in said chamber for shifting said adjusting means to conversely decrease" or increase the time of said periodic opening.

3. The combination defined by claim 2 characterized by said'chamber having a boiler associated therewith, and said shifting means including means responsive to the increase or decrease in pressure in said boiler.

4. The combination defined by claim 2 characterized by said mechanism including a sliding. shaft having an elongated tapered cam thereon to effect said variation.

BEN LOVE.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 1,840,588 Knox Jan. 12, 1932 1,847,260 Pardee Mar. 1, 1932 1,849,347 Dale Mar. 15, 1932 1,948,536 Noack Feb. 27, 1934 2,101,412 Pescara Dec. 4, 1937 2,102,121 Janicke Dec. 14, 1937- 2,227,666 Noack Jan. 7, 1941 2,227,896 Fitzgerald Jan. 7, 1941 FOREIGN PATENTS Number Country Date 496,692 France Aug. 12, 1919 511,356 France Sept. 23, 1920 239,150 Great Britain 1925 239,434 7 Great Britain 1925 30,554 France Mar. 30, 1926 675,693 France 1930 

